The present invention pertains to networking systems and pertains particularly to multiple protocol handshaking between systems.
When two host systems are communicating via a cable, each host system typically includes a transceiver that converts electrical signals received from the host system to signals that are suitable for the cable. Each transceiver also converts signals received from the cable to electrical signals usable by the host system. Generally, the transceiver can convert the signals one bit at a time or the transceiver can encode/decode the signals. In addition, the transceiver can be an electro-optic transceiver (which converts electrical signals to optical signals and vice versa) or an electrical transceiver (which converts electrical signals of one format to another format and vice versa). Typically, the “one bit at a time” transceiver allows handshaking to occur directly between two host systems and the “encoding/decoding” transceiver does not. Typically, the electro-optic transceiver allows the use of a receiver status signal to be sent when a cable connection is detected and the electrical transceiver does not.
For example, in 1000BASE-X systems transceivers typically perform the conversion one bit at a time. The transceiver can be electro-optical or electrical in nature. When the transceiver is electro-optical, the two communicating systems are connected with a fiber optic cable. The electro-optic transceiver converts each bit in the electrical signal received from the host system to a bit in an optical signal to be sent across the fiber optic cable. Each electro-optic transceiver also converts optical signals received from the fiber optic cable to electrical signals used by the host system. When an electro-optic transceiver first receives light from a source at the other end of the fiber optic cable, the electro-optic transceiver updates its receiver status signal. When both electro-optic transceivers forward to their respective host systems a receiver status signal that indicates the reception of optical power the two host systems perform their handshaking protocol to establish a link.
Whenever a fiber optic cable link between two electro-optic transceivers is broken, each electro-optic transceiver changes its receiver status signal to indicate optical power is no longer being received. When the fiber optic cable link between two electro-optic transceivers is restored, each electro-optic transceiver changes its receiver status signal to indicate the reception of optical power and the systems again perform handshaking.
When two host systems are communicating via electrical (e.g., copper-based) cables, each host system typically includes an electrical transceiver that converts electrical signals in a format used by the host system to electrical signals in a format appropriate to be sent across the electrical cables. Each electrical transceiver also converts electrical signals received from the electrical cables to electrical signals in a format used by the host system. A typical 1000BASE-X transceiver converts data one bit at a time. Typically, in systems based on electrical cable, there is nothing equivalent to a receiver status signal that indicates the reception of optical power. This results in an incompatibility between protocols used between host systems using two electrical transceivers to exchange information over electrical cables and protocols used between host systems using two electro-optic transceivers to exchange information over a fiber optic cable.
If 1000BASE-X host systems are communicating and non-1000BASE-X transceivers that encode/decode data are used, then direct handshaking between the host systems is not possible. For example, if 1000BASE-T electrical transceivers are used in two communicating 100OBASE-X systems, the data from a host system is encoded by the 1000BASE-T transceiver and the special handshaking codes sent by the system are not passed through the 1000BASE-T transceiver. In addition, as in the case when a 1000BASE-X electrical transceiver is used, the receiver status signal does not exist when the 1000BASE-T electrical transceiver is used in the system.
For further information, see, for example, the IEEE Std. 802.3, 2000 Edition, Part 3: Carrier sense multiple access with collision detection (CSMA/CD) access method and physical layer specifications, Clause 36 and Clause 37, in which pertinent parts of the 1000BASE-X protocol are discussed, and Clause 40 and Clause 28, in which pertinent parts of the 1000BASE-T protocol are discussed.